As is known in the art, Wireless Local Area Networks (WLAN) are becoming more and more popular nowadays due to their easy deployment and wide spread of WiFi interface cards. A Wi-Fi Alliance report finds that 1.2 million 802.11 chipsets will be produced in 2006.
Parallel to technological development, a flurry of analytical studies appeared in communication literature.
Experimental results and theoretical studies show that wireless networks may enter a saturation regime characterized by a highly suboptimal medium utilization. More specifically, standard rate adaptation mechanisms reduce transmission rates when multiple packet loss occurs. Yet if the packet loss is due to collision rather than bad channel (which is the working assumption for the rate adaptation mechanism) then the controller induces a higher probability of collision which snowballs in turn into an even lower throughput. Such a mechanism is used by the Automatic Rate Fallback (ARF) algorithm used in WLAN-II products from Lucent which assumes all packet losses are due to bad channel.
This scenario of use motivates us to analyze and build a packet loss detection mechanism which predicts, based on available information, the cause for packet loss: either packet collision, or bad channel.
Recently, there have been proposed two mechanisms to address this issue. Our method is different from these two as described in the next section.
Whitehouse et al. [K. Whitehouse et al, Exploiting the Capture Effect for Collision Detection and Recovery, The 2nd IEEE Workshop on Embedded Networked Sensors (EmNetS-II), May 2005] assume the packet header may be deciphered correctly by a receiving station (device, or access point), and hence based on the packet termination, one can infer whether there was a packet collision, or too low signal-to-noise ratio (SNR). However this may not happen in a large range of noisy condition, as showed by Yun et al [J.-H. Yun, S.-W. Seo, Collision Detection based on Transmisión Time Information in IEEE 802.11 Wireless LAN, Proceedings of the 4th Annual Inter. Conf. on Perv. Comp. Comm. Workshop (PERCOMW'06), 2006]. Instead, Yun et al, propose a deterministic scheme through which participating stations include temporal information relative to packet transmission/reception that can be used to predict when a collision happens. This approach, albeit very precise, has the back draw of modifying the MAC implementations on participating wireless stations.